In three experiments, we investigated whether the production of subject-verb number agreement is affected by the phonological realization of grammatical information. Speakers repeated and completed German or Dutch noun phrases along the lines of The position against the demonstrations. We varied the number of the subject noun (position) and the local noun (demonstrations), as well as the number ambiguity of the subject noun's determiner and the case ambiguity of the local noun phrase. Sentence completions more often contained a verb of the wrong number if the subject and the local nouns mismatched in number than if they matched. Experiments 1 and 2, in German, showed a stronger number mismatch effect if the local noun phrase was ambiguous between the nominative and the accusative cases. Experiment 3, in Dutch, showed a stronger mismatch effect if the subject noun's determiner was ambiguous in number. We conclude that morphophonological factors affect the implementation of agreement during grammatical encoding.